The term “process variable” generally refers to a physical or chemical state of matter or conversion of energy. Examples of process variables include pressure, temperature, flow, conductivity, pH, and other properties. The term “process measurement” refers to the acquisition of information that establishes the magnitude of process quantities. Pressure is considered a basic process variable in that it is used for the measurement of flow (the difference of two pressures), level (head or back pressure), and even temperature (fluid pressure in a thermal system).
An industrial process transmitter generally includes a transducer or sensor that responds to a measured variable with a sensing element that converts the variable to a standardized transmission signal, e.g., an electrical or optical signal where air pressure, that is a function of the measured value. Industrial process pressure transmitters are used to measure pressure within industrial processes such as slurries, liquids, vapors and gasses in chemical, pulp, petroleum, gas, pharmaceutical, food, and other fluid processing plants. Industrial process fluid transmitters are often placed near the process fluids, or in field applications. Often, these field applications are subject to harsh and varying environmental conditions that provide challenges for designers of such transmitters.
Process fluid pressure transmitters are generally coupled to the process by virtue of a manifold. The manifold routes the process fluid from one or more process fluid inlets to one or more process fluid outputs, which process fluid outputs are arranged, or otherwise configured in a standardized manner to match, or otherwise cooperate with, the location of process fluid inputs on pressure sensor modules of process pressure transmitters.
One particular type of manifold is known as a coplanar style manifold. Such manifolds are available from Rosemount, Inc. of Eden Prairie, Minn. under the trade designation Model 305 and Model 306 manifolds. Each of the models 305 and 306 manifolds can be ordered in a variety of configurations. Generally, a manifold will have at least one valve that provides pressure transmitter isolation. This isolation can allow the process pressure transmitter to be removed and repaired and/or replaced while the valve maintains isolation from the process. Coplanar manifolds can also be provided with two, three and five valve configurations. All such coplanar manifolds generally provide a plug for drain/vent capabilities. Coplanar manifolds can allow a number of process fluid pressures to be coupled to a process fluid pressure transmitter through a single, unitary manifold. Such a configuration can reduce installation costs and technician time, as well as provide an extremely robust process fluid connection.
Any interface between two surfaces which contacts process fluid, and extends to an outer surface that is in contact with the ambient environment may create a source of process fluid leaks. In order to remedy process fluid leaks, a field technician or other skilled worker may be required to diagnose and repair the problem. Providing a process pressure transmitter manifold that is less susceptible to leaks would benefit the process measurement and control industry.